Abstract: An interferometer is provided that includes a first path and a second path. The first path is configured to propagate an electro-magnetic signal at a first wavelength. The second path is configured to convert a portion of the electro-magnetic signal from the first wavelength to a second wavelength for processing and is configured to convert the portion of the electro-magnetic signal from the second wavelength back to the first wavelength for interference with the electro-magnetic signal of the first path. The first wavelength may be an optical wavelength or any other suitable wavelength of the electro-magnetic spectrum. The second wavelength, which is different than the first wavelength, also may be any suitable wavelength of the electro-magnetic spectrum.

Abstract: An optical device includes a substrate with first and second arrays of optical couplers located along a planar surface thereof. The optical couplers of the first array are laterally arranged along the surface to end-couple in a one-to-one manner to corresponding optical cores of a first multi-core fiber whose end is facing and adjacent to the first array. The optical couplers of the second array of optical couplers are laterally arranged along the surface to end-couple in a one-to-one manner to corresponding optical fiber cores of one or more optical fiber ends facing and adjacent to the second array. An optical switch network is optically connected to selectively couple some of the optical couplers of the first array to the optical couplers of the second array in a one-to-one manner.

Abstract: One aspect provides an optical device. The optical device includes a first and a second array of optical couplers, a plurality of waveguides and a plurality of pump couplers located over a surface of a substrate. The optical couplers of the first array are able to end-couple in a one-to-one manner to the optical cores of a first multi-core fiber having an end facing and adjacent to the first array and the surface. The optical couplers of the second array are able to end-couple in a one-to-one manner to optical cores having ends facing and adjacent to the second array. The plurality of optical waveguides connects in a one-to-one manner the optical couplers of the first array to the optical couplers of the second array. Each optical waveguide has a pump coupler connected thereto between the ends of the waveguide.

Abstract: An optical device includes an array of optical grating couplers and a plurality of single-core fiber couplers located over a planar substrate. The optical grating couplers of the array are located to optically couple in a one-to-one manner to optical cores of a multi-core fiber or optical cable having an end located adjacent to the surface. Each single-core fiber coupler includes a planar optical waveguide connecting a corresponding one of the optical couplers of the array to an edge of the substrate.

Abstract: Duobinary and NRZ modulation of an X-Gb/s optical signal is achieved with a lumped element InP Mach-Zehnder device configured to operate at X/k-Gb/s where k>1 and arranged in a push-pull configuration.

Abstract: A method of optically equalizing a multi-level (amplitude or phase) optical signal through the effect of an optical equalizer wherein the optical equalizer (OEQ) is placed at either a transmission end or a receiver end of the optical communications link and a tap delay characteristic of the OEQ need not be determined by symbol spacing, rather it may advantageously be adjusted to desirably compensate non-linear mapping performed in the modulation process or simultaneous operation on a plurality of wavelength division multiplexed (WDM) channels.

Abstract: A scheme is described for mitigating the effects of polarization-mode dispersion (PMD) in a wave-division multiplex (WDM) optical communication system having one or more transmission links with one or more quasi-static waveguide sections coupled by one or more non-static coupling sections. A transmitter is coupled to the transmission link and is adapted to transmit optical signals through the transmission link with wavelength channel spacing of the optical signals greater than about the PMD correlation bandwidth of at least one of the one or more quasi-static waveguide sections, so that the PMD induced outage probability for the system is optimized.

Abstract: A bandstop filter method and system for suppressing ASE noise is disclosed. In one embodiment of the bandstop filter system, there is provided a first switch, having an input port for receiving an optical signal, and two output ports; a bandstop filter coupled to a first of the two output ports of the first switch; and a second switch, having two input ports and one output port, wherein a first of the two input ports of the second switch is coupled to the bandstop filter and a second of the two input ports of the second switch is coupled to a second of the two output ports of the first switch.

Abstract: A high-speed optical modulator constructed from a number of lower speed intensity modulators integrated onto a single optical chip.

Abstract: A method of optically equalizing a multi-level (amplitude or phase) optical signal through the effect of an optical equalizer wherein the optical equalizer (OEQ) is placed at either a transmission end or a receiver end of the optical communications link and a tap delay characteristic of the OEQ need not be determined by symbol spacing, rather it may advantageously be adjusted to desirably compensate non-linear mapping performed in the modulation process or simultaneous operation on a plurality of wavelength division multiplexed (WDM) channels.

Abstract: Severe inter-symbol interference (ISI), introduced by narrow-band optical filtering in high spectral efficiency wavelength-division multiplexed (WDM) systems to avoid coherent WDM crosstalk, can be substantially mitigated by the use of maximum-likelihood sequence estimation (MLSE) reception. Compared to conventional threshold detection, the use of an MLSE receiver allows, for example, a 22% reduction in optical receive filter bandwidth. For tight optical filtering, the MLSE receiver benefits from taking into account noise correlation. MLSE receivers with one and with two samples per bit are described and it is shown that while oversampling is beneficial for wide-band optical filters, the benefit goes away for narrow-band optical filtering, thereby facilitating MLSE design for rates beyond 10 Gb/s.

Abstract: Duobinary and NRZ modulation of an X-Gb/s optical signal is achieved with a lumped element InP Mach-Zehnder device configured to operate at X/k-Gb/s where k>1 and arranged in a push-pull configuration.

Abstract: A high-speed optical modulator constructed from a number of lower speed intensity modulators integrated onto a single optical chip.

Abstract: An apparatus and method for tunably delaying a signal and using that delayed signal in a duobinary transmitter is described. The transmitted duobinary signal is representative of the binary signal, and is formed by, among other things, introducing into a copy of the binary signal a delay that may be adjusted to be greater than or less than the bit period of the signal. Once the binary signal has been converted into a duobinary signal, it may then be converted into an optical duobinary signal. Alternatively, the conversion from binary to duobinary in accordance with the invention may be performed in the optical domain.

Abstract: Methods and apparatus for aligning the transmitters of two or more bidirectional ports of an integrated circuit (IC), particularly an application-specific IC (ASIC) or field-programmable gate array (FPGA). Misalignment of two or more transmitters is determined by the IC itself without the use of external test equipment. Receivers of the bidirectional ports whose transmitters are to be aligned are used by the IC to detect misalignment. Any misalignment of the receivers is also determined and either eliminated or taken into account when aligning the associated transmitters. Variants for ICs with and without internal loop-back capability and for ICs with and without differential outputs are described.

Abstract: A WDM communication system having two optical-frequency comb sources (OFCSs) that are substantially phase-locked to one another, with one of these OFCSs used at a transmitter to produce a WDM communication signal and the other OFCS used at a receiver to produce multiple local-oscillator signals suitable for homodyne detection of the WDM communication signal received from the transmitter. In one embodiment, the transmitter has (i) a first OFCS adapted to generate a first frequency comb and (ii) an optical modulator adapted to use the first frequency comb to generate a WDM communication signal for transmission to the receiver, this WDM signal having at least two beacon lines. The receiver has a second OFCS adapted to produce a second frequency comb such that the second frequency comb has at least two comb lines having the beacon frequencies, the phases of which comb lines are locked to the phases of the beacon lines of the received WDM signal.

Abstract: In an over-sampled maximum-likelihood sequence estimation (MLSE) receiver system, the optimal sample spacing is determined for a variety of conditions. In an illustrative implementation, the system includes an optical filter for tightly filtering an incoming optical data signal with an on-off-keying (OOK) non-return-to-zero (NRZ) format, followed by an optical-to-electrical converter, an electrical filter, a sampler, and a MLSE receiver. The sampler samples the filtered electrical data signal twice each bit period with unequal sample spacings. For wide optical filtering bandwidths, the optimal sample spacing occurs at less than 50% of a bit period. For narrow bandwidths, the optimal sample instances occur closer to the maximum eye opening.

Abstract: A bandstop filter method and system for suppressing ASE noise is disclosed. In one embodiment of the bandstop filter system, there is provided a first switch, having an input port for receiving an optical signal, and two output ports; a bandstop filter coupled to a first of the two output ports of the first switch; and a second switch, having two input ports and one output port, wherein a first of the two input ports of the second switch is coupled to the bandstop filter and a second of the two input ports of the second switch is coupled to a second of the two output ports of the first switch.

Abstract: A scheme is described for mitigating the effects of polarization-mode dispersion (PMD) in a wave-division multiplex (WDM) optical communication system having one or more transmission links with one or more quasi-static waveguide sections coupled by one or more non-static coupling sections. A transmitter is coupled to the transmission link and is adapted to transmit optical signals through the transmission link with wavelength channel spacing of the optical signals greater than about the PMD correlation bandwidth of at least one of the one or more quasi-static waveguide sections, so that the PMD induced outage probability for the system is optimized.

Abstract: Randomized load balancing across a selected subset of routing nodes is shown to achieve near-optimal usage of network resources, yet alleviates “single point of failure” problems associated with existing hub routing techniques.